Reactions of Arylbiguanides with Benzoin at the pH of the Biguanide Bases

Article abstract of DOI:10.1007/BF00810471

Arylbiguanides 2 a-e react with benzoin (1) at the pH of the base to two different products. 1 undergoes in presence of the base 2 a-e oxidation to benzil and benzoic acid, which reacts fast with the arylbiguanides 2 a-e to yield N-<4-(arylamino)-6-phenyl-1,3,5-triazine-2-yl>benzamides 3 a-d.After lowering the pH of the reacion mixture, the bases 2 b-e react with benzil to yield 2-<1-aryl-5-oxo-4,4-diphenyl-2-imidazoline-2-yl>guanidine 4 b-e.The mechanism of the formation is discussed.The structure of 4b was established from a single crystal x-ray structure analysis.The analysis was carried out at 100 K: C23H21N5O, M_r=383.5, monoclinic, C 2/c, a=15.842(6), b=8.419(3), c=30.223(10) Angstroem, β=98.44(3) deg, V=3987.3(9) Angstroem³, Z=8, d_x=1.277 g/cm³, μ=0.81 cm^-1, R=5.89percent, R_w=4.97percent (1537 observations, 233 parameters).Keywords.Benzoin, reaction with arylbiguanides; Triazines (N-<4-(arylamino)-6-phenyl-1,3,5-triazine-2-yl>benzamide); Imidazoles (2-<1-aryl-5-oxo-4,4-diphenyl-2-imidazoline-2-yl>guanidine); Synthesis; NMR-data; X-ray analysis.